How accurate is the speedo?

[buzzy]

Actually, when I got mine it needed reseting a few times. It's been fine ever since. Well it's the normal 5-7mph over.

[darkSol]

For the past month or so I'll do the reset procedure, start the car, let her warm up in the garage for a minute or two and then start driving (She has to warm up - my entire commute is 4.2 miles. She'll jerk and stutter if I just drive her bone cold in the morning - NOT a fun drive).

Anyway the speedo is great for the next two miles... registering 25-35 mph dead-on as I get to the (60mph) highway. I perform my left turn and accelerate to merge with traffic. Right up to 60-65 mph indicated.

Even though my highway commute is only 3 miles - I usually catch up to traffic and have to let off the gas or even brake several times.

Almost every single time I do this sequence "gas/let off/gas/let off" the mph's drop. Substantially.

This morning by the time I got to my off ramp the speedo was registering 28 mph... when Mr. Garmin was registering 65 mph.

Totally bizarre.

I'll check/brake clean the rear hubs/pickup sensors just to make sure that they're working correctly.

Now that I'm thinking about it I should actually connect and DL-1 datalog all 4 of the wheel speed sensors.... hmm.

Anyone else ever have this problem?

[darkSol]

My problem has been fixed.

When I had the new ACT XT-SS clutch / Fidanza flywheel installed two weeks ago the mechanic noticed some fraying of the left rear (speedo pickup) ABS sensor wiring. He snipped it, resoldered, double shrink wrapped it and it's back to it's normal 7% over reading... which is better than 0 or 100 or 30 or whatever it wants to send to the speedo.

I'm going to keep an eye on this but it's been golden since I got the car back.

[shay2nak]

will switching to 15/16" wheels solve the problem?

[AtlantaLotusLove]

As an update to this thread for those with the 0 mph speedo error:

After a charger hooked to my '05's battery had short-circuited, my speedo was reading 15 mph, and my tach was reading 1000 rpm when sitting still. The problem resolved permanently after I disconnected the battery neg. terminal and reconnected it, as suggested by Randy on another thread.

I also have the calibration problem (10% high speedo at all speeds), which is a separate issue, as discussed hear extensively already. I can live with that!